Place theory is most appropriate for explaining how infants:

Place theory is a fundamental concept in auditory perception that explains how we perceive different pitches of sounds. This theory posits that different frequencies of sound waves stimulate different places along the cochlea, which is part of the inner ear. Specifically, higher frequency sounds activate hair cells located closer to the base of the cochlea, while lower frequencies stimulate hair cells further along the cochlea towards the apex.

Infants, like adults, use this mechanism as they process auditory stimuli. The application of place theory in the context of infants suggests that they are capable of discerning pitch through the specific region of the cochlea that is activated by sound waves. This ability to process pitch is crucial for language development and communication skills.

Other options touch upon different senses or associative processes that are not as relevant to place theory. For instance, associating a red light with auditory stimuli pertains to the concept of classical conditioning rather than auditory perception. Distinguishing features of a face relates to visual processing, and perceiving the distance of a visual stimulus involves depth perception, which is governed by different mechanisms. Place theory specifically pertains to auditory perception, making it the most appropriate explanation for how infants process pitch.